Control valves and shut-off valves are generally provided with a control device in the form of a hand control, which is mounted directly on the valve spindle. A device for remote control operation can be entirely mechanical and for example, be formed of one or more shafts, which are connected to the valve spindle via a cardan joint or be electronic and be formed of an electric motor, which via a gear reduction is connected to the valve spindle, and the motor is controlled, for example, by electrical signals which, via a relay closes the current to the motor. The remote control is actuated for example by the valve being located in a place which cannot be reached without great difficulty inter alia on pipes, located high above the ground and in closed spaces, as for example cisterns. It has also proven difficult to arrange remote controls with lead-ins in for example cisterns in which a fluid or a gas is under pressure and also on long distances where many moving direction of the transmission are demanded.
Quick closing valves to a certain extent have an outstanding position in the applications, where the present invention is advantageous. Quick closing can either be done manually or automatically, e.g., when damage has occurred and it is desired to immediately stop the gas or liquid flow. A complete mechanical excess flow valve is described in Swedish Patent 7413120 and comprises a valve body on a valve push rod mounted in a tube and movable in the longitudinal direction of the tube towards a ring-shaped seat. The push rod is in connection with a spring on the outside of the tube via a link mechanism, where one of the link arms extends through the wall of the tube via a sealing box. When there is a pipe rupture at a point downstream of the excess flow valves in the flow direction, the flow rate in the tube increases and a low pressure arises on the underside of the valve body. When the low pressure causes a force on the valve body, which via the link mechanism comprises the spring, the valve body is displaced towards the seat, and the tube is closed. The size of the spring force is adjustable and thus the excess flow valve can be closed at different flow rates.
A disadvantage with the conventional excess flow valve is that the tightening box in the tube wall as time goes becomes worn and begins to leak. Another disadvantage is that there is no easy way to change the adjustment in the valve using remote control. A further disadvantage is that the valve cannot be opened without great difficulty if it has been closed by mistake. Then the pressure in front of the valve has to be lowered, e.g. by using a special unloading valve before the excess flow valve can be opened again. In the same way another conventional excess flow valve works, which is not adjustable from the outside of the tube but is equipped with a spring, which directly works on the valve body inside the tube.